[lurkingknight]

a flathop nub is generally taller than a standard nub or the prommy bridge nub. It has to be taller because there's thickness on a standard bucking where the mound is. The rhop patch fills this void and you shave the mound off the bucking.

A flat hop setup has no mound, just a cylinder of rubber so if you used a regular nub, your hopup adjustment wheel would bottom out and there would still be no protrusion of the rubber material into the barrel to initiate hop.

Rhop isn't magical it still works the same way as a standard hop setup, it just replaces the mound with something that's a far more consistent shape. You can use a standard cylindrical nub, a block of eraser, HS5 m-nub, or a flathop nub. Though block shaped nub replacements work best once it's all working properly.

Depending on how much protrusion you get is how you know you need to sand more on the patch which is what can make an r-hop install tedious.